EP0905642B1

EP0905642B1 - A light source module for a scanning apparatus and a scanning apparatus with the light source module

Info

Publication number: EP0905642B1
Application number: EP98304263A
Authority: EP
Inventors: Masanori C/O Fujitsu Limited Ohkawa; Toshiyuki C/O Fujitsu Limited Ichikawa; Hiroshi c/o Fujitsu Limited Watanuki; Kozo C/O Fujitsu Limited Yamazaki
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 1997-09-30
Filing date: 1998-05-29
Publication date: 2006-08-02
Anticipated expiration: 2018-05-29
Also published as: US20010023894A1; EP0905642A3; CN100440244C; CN1305294C; CN1509062A; CN1254947C; EP0905642A2; JPH11112097A; CN1213244A; CN1881233A; DE69835405T2; DE69835405D1; US6840452B2; US6283373B1

Description

The invention relates to a light source module for a scanning apparatus such as a bar code reader.
Recently, point-of-sale systems (POS systems) have become common in stores. In a POS system a bar code reader reads a bar code provided on an article. According to the POS system, check-out work is carried out only by scanning a beam emitted from a bar code reader. Thus, the work of operator (salesclerk) is reduced by using a bar code reader.
A bar code reader generally includes a light source for emitting a beam, an arrangement for generating a scanning beam by reflecting the beam from the light source, such as a rotating polygon mirror, a plurality of mirrors for reflecting the scanning beam and for dividing the scanning beam to provide a set of scanning lines outside of the bar code reader. The return beams reflected by a bar code on an article are condensed by a concave mirror or a condenser lens onto a light receiving device, such as a photodiode which generates an electrical signal corresponding to the return beams received by the light receiving device. These elements are sealingly contained within a housing to provide an optical unit.
Such an apparatus for reading a bar code is a kind of a scanner apparatus, similar to a scanner device in a laser printer or a copy machine, and is often referred to a POS scanner or a bar code scanner. A laser diode is often used as a light source because of its compactness, low power consumption, and cost while a gas laser beam (for example, He-Ne laser beam) was originally used.
JP 08 248285 discloses a light source module, suitable for a scanner, comprising a light source module comprising: a laser diode for emitting a laser beam; a circuit board including the laser diode, a driver circuit for the laser diode, and a connector for receiving a power supply for driving the laser diode from an electric power source; and means for shaping the laser beam emitted by the laser diode.
A laser diode has a problem that its life is shorter than a gas laser so that a bar code reader with a laser diode must be designed and used while considering replacement of the light source. Further, there is a problem that static electricity may damage a semiconductor laser.
In previously-proposed scanner apparatus, a light source is provided by a VLD (Visible Laser Diode) module which includes a laser beam source, a lens and an aperture for shaping a beam.
When replacing a laser diode, the VLD module is replaced with the laser diode. The VLD module is contained within the housing of the optical unit. Thus, the housing of the optical unit must be opened to replace the VLD module. This work must be carried out in a clean room to prevent dust, which may harmfully effect the optical characteristics of the scanner, from entering the optical unit. There is also a problem that the bar code reader to be mended cannot be used during the replacement of the VLD module.
US-A-4926433 discloses a housing, made of insulating material, for a light source module, but the housing of the prior art does not surround the circuit board, nor does it serve to protect the circuit board from static electricity.
GB 2287577 discloses a light source module comprising: a laser diode for emitting a laser beam; a circuit board including the laser diode, a driver circuit for the laser diode, and a connector for receiving a power supply for driving the laser diode from an electric power source; means for shaping the laser beam emitted by the laser diode, which beam shaping means comprise a lens for condensing the laser beam emitted by the laser diode and means defining an aperture through which the laser beam propagates from the lens; a housing for containing the beam shaping means and the circuit board except for a portion of the circuit board where the connector is mounted; a mount for securing the circuit board inside the housing; and a lens holder for holding the optical axis of the lens in alignment with the aperture.
Such a light source module may be replaced more easily. Moreover, the possibility of damage to the laser diode by static electricity may be removed or reduced, since the operator can replace the light source module without touching the laser diode.
According to the present invention, there is provided a a light source module comprising: a laser diode for emitting a laser beam; a circuit board including the laser diode, a driver circuit for the laser diode, and a connector for receiving a power supply for driving the laser diode from an electric power source; means for shaping the laser beam emitted by the laser diode, which beam shaping means comprise a lens for condensing the laser beam emitted by the laser diode and means defining an aperture through which the laser beam propagates from the lens; a housing for containing the beam shaping means and the circuit board except for a portion of the circuit board where the connector is mounted; a mount for securing the circuit board inside the housing; and a lens holder for holding the optical axis of the lens in alignment with the aperture;
characterised in that: the housing is made of electrically insulating material; the mount includes a bore extending through the mount to open to the laser diode on the circuit board; and in that the lens holder is fitted into the bore of the mount to slide along the bore, the movement of the lens holder within the bore along the longitudinal axis of the bore adjusting the position of the focal point of the laser beam.
Reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a front view of a bar code reader incorporating an embodiment of the present invention;
Figure 2 is a side section of the bar code reader of Figure 1;
Figure 3 is a perspective view of a housing of a VLD module embodying the present invention;
Figure 4 is a side view of the housing of Figure 3;
Figures 5A and 5B are top and bottom views of the housing of Figure 3, respectively;
Figure 6A and 6B are perspective and side view of a cover of the VLD module;
Figure 7 is a side view of the cover of Figure 6A;
Figure 8 is a bottom view of the cover of Figure 6A;
Figure 9 is a perspective view of the housing and cover illustrating the assembling thereof;
Figure 10 is a perspective view of the bottom a mount of the VLD module to which a lens and an aperture are mounted;
Figures 11A and 11B are front and bottom views of the mount of Figure 10;
Figure 12 is a side view of the mount;
Figure 13 is a perspective view of a lens holder of the VLD module;
Figures 14A and 14B are bottom and side views of the lens holder;
Figure 15 is a perspective view of the mount and the lens holder, illustrating the assembling thereof;
Figures 16A to 16C are front, plan and side views of the mount, lens holder and a circuit board which are assembled;
Figure 17 is a front section of the VLD module;
Figure 18 is a side section of the VLD module;
Figure 19 is a front view of an optical unit of the bar code reader;
Figure 20 is a side view of the optical unit of Figure 19;
Figure 21 is top view of the optical unit of Figure 19;
Figure 22 is a back view of a housing of the optical unit of Figure 19;
Figure 23 is an interior elevation of the optical unit of Figure 19;
Figure 24 is a side section of the housing of the optical unit of Figure 19 ;
Figure 25 is a top view of the housing of the optical unit of Figure 19;
Figure 26 is a section of the housing of the optical unit of Figure 19;
Figure 27 is back view of.the optical unit of Figure 19, illustrating a recess for receiving a circuit board;
Figure 28 is a side view of the housing of the optical unit, illustrating the VLD module mounted to the housing;
Figure 29 is a top view of the housing of the optical unit, illustrating the VLD module mounted to the housing;
Figure 30 is an enlarged top view of the VLD module mounted to the housing;
Figure 31 is an enlarged section of the VLD module mounted to the housing;
Figure 32 is an enlarged back view of the VLD module mounted to the housing;
Figure 33 is a block diagram relative to the VLD module of the present invention; and
Figure 34 is a block diagram similar to Figure 33 according to a previous proposal.

In the following description, an embodiment of the present invention is applied to a bar code reader. However, an embodiment of the present invention can also be applied, for example, to a scanner device in a laser printer or a copy machine, etc,.
Figure 1 is a front view of a bar code scanner incorporating an embodiment of the present invention. Figure 2 is a side section showing the internal arrangement of the bar code scanner.
The bar code scanner is of an upright type and is mounted to a top surface 10 of a table such as a cashier counter. The housing of the scanner includes first and second openings 11 and 12 through which first and second scanning beams propagate outside of the housing, respectively. The first opening is perpendicular to the top surface 10. The first scanning beam horizontally propagates through the first opening 11 while the second scanning beam propagates obliquely downwardly through the second opening 12. The first and second beams intersect in front of the first opening 11.
A bar code (not shown) on an article (not shown) is irradiated by at least one of the first and second beams when the bar code passes the reading area where the first and second beams intersect in front of the bar code reader. A bar code reader with a single opening cannot read a bar code if an operator does not orient the bar code to the window accurately. On the other hand, in a bar code reader embodying the present invention, the provision of two sets of openings and beams enables the scanner to read the bar code if an operator does not orient the bar code to the first or second opening accurately.
A display 13, for indicating the name and the price corresponding to a bar code and the total of the purchase, is provided to the top of the scanner. The display 13 includes first and second indicators 13a and 13b, respectively. The first and second indicators 13a and 13b are oriented to the operator of the scanner and the customer. The first and second indicators 13a and 13b may indicate the same information.
The scanner further includes an optical unit 14 and a VLD (Visible Laser Diode) module 15, as a light source module. The VLD module 15 is mounted outside of the optical unit 14 by screws 16 (only one of which is shown in the drawings). A buffer or a damper 17 of a resilient material, such as a rubber or a urethane, is provided between the VLD module 15 and the optical unit 14.
With reference to Figure 23, within the optical unit 14, a polygon mirror 93, a plurality of mirrors 96a to 96h for providing a set of scanning lines outside of the scanner by reflecting the scanning beam from the polygon mirror 93, and a concave mirror 94 for condensing the reflected beam from the bar code to an optical receiver 98 such as a photodiode are provided.
The VLD module 15 includes a housing portion 20 shown in Figures 3 to 5B, and a cover 30 shown in Figures 6A to 8, both of which are made of molded resin. The housing portion 20 includes an aperture 21 through which a laser beam is emitted from a laser diode contained in the housing 20 and 30 to the polygon mirror 93 as described hereinafter. It should be noted that although the housing portion 20 is shown in Figures 3, 4, 5 and 9, so that the aperture 21 is laterally oriented, the VLD module 15 attached to the optical unit 14 so that the aperture 21 is oriented to the bottom of the unit 14 as shown in Figure 20. In this specification, "top" and "bottom" are defined as the orientation shown in the drawings.
The cover 30 comprises a base 31, and a pair of mounting members 32 extending from the sides of the base 31. The base 31 includes a ridged portion 33 on the base 31, a pair of through holes 34, a cutout 36 for positioning the VLD module to the optical unit 14, and a hook 35 adjacent to the cutout 36. Each of the mounting members 32 includes a through hole 32a into which a screw 16 (Figure 2) is inserted to secure the VLD module to the optical unit 14.
The cover 30 is connected to the housing portion 20 to close the opening of the housing portion 20, as shown in Figure 9, to provide a housing of the VLD module 15.
Shown in Figures 10 to 12 is a mount 40 for securing the laser beam source inside of the housing of the VLD module. The mount 40 includes two pairs of threaded holes 41a and 41b and a recess 45 adapted to fit the ridged portion 33 on the top surface of the base 31 of the cover 30, and may be made of die cast aluminum. The threaded holes 41a receive screws 71 (Figure 18) which are inserted into the through holes 34 of the cover 30 to secure the mount 40 to the base 31 of the cover 30. The threaded holes 41b receive screws 63 (Figures 16A and 16B) to secure.a printed circuit board as mentioned hereinafter.
The mount 40 further includes a bore 42 into which a lens holder 50 (Figures 13 to 15) is fitted, and a threaded hole 43 into which a screw 64 (Figures 16A and 16C) is threaded to lock the lens holder 50. The lens holder 50 is shaped in the form of a cylinder which includes a bore 51 and a flattened portion 52 to which the tip of the screw 64 abuts to lock the holder 50.
The lens holder 50 holds an aperture plate 53 which includes an aperture 53a and a lens 54 which is fixed to the inside of the bore 51 (Figures 14A and 14B). The aperture 53a shapes the beam to provide a desirable beam section. The configuration of the aperture 53a can be selected according to the desirable section of the laser beam while the aperture 53a has a rectangular configuration in the embodiment shown in Figures 14A and 14B. The lens 54 adjusts the focal point of the beam. The aperture plate 53 and the lens 54 adjust the diameter of the laser beam.
The lens holder 50 is slidably fitted into the bore 42 of the mount 40 as shown Figure 15. The movement of the lens holder 50 within the bore 42 in the longitudinal direction shown by an arrow A in Figure 15 changes the position of the focal point of the laser beam within the reading area in front of the bar code reader. Changing the position of the focal point adjusts the diameter of the laser beam within the reading area. The adjustment of the lens beam diameter is a critical issue since the diameter is the factor which defines the capability of reading a bar code (resolution for reading). The smaller the diameter, within an appropriate range, the narrower the bars of a bar code which can be read. The VLD module 15 comprises the lens holder as means for shaping the laser beam separately from the mount 40, which facilitates the adjustment of the diameter of the laser beam.
With reference to Figures 16A to 16C, a circuit board 61 is attached to the mount 40 by the pair of screws 63 threaded into the holes 41b of the mount 40. The circuit board 61 includes a laser diode 62 secured to the circuit board 61, and a driver circuit (not shown) for driving the diode laser 62.
The circuit board 61 is attached to the mount 40 so that the optical axis of the beam from the laser diode 62 is aligned with that of the lens holder 50, in particular, that of the aperture 53a and the lens 54 held by the lens holder 50.
A laser diode has a characteristic that the power of the emitted beam is not uniform from one to the other. Thus, a variable resistor 65 is provided for adjustment of the beam power emitted from the laser diode 62 so that the fluctuation in capability of reading between the scanners decreases.
A connector 66, for connecting the laser diode 62 to a power source, is also provided on the circuit board 61.
With reference to Figures 17 and 18, the circuit board 61, except for the connector 66, the mount 40 and the lens holder 50 are contained within the housing 20 and 30 to provide the VLD module 15. The mount 40 is disposed on the cover 30 in place by the fitting between the recess 45 (Figure 10) provided in the mount 40 and the ridged portion 33 on the top surface of the base 31 of the cover 30. The mount 40 is secured to the cover 30 by screws 71 which are inserted into the through holes 34 of the cover 30 and threaded into the threaded holes 41a of the mount 40. Thus, the laser diode 62 is disposed relative to the mount 40 and the lens holder 50.
The laser diode 62 is contained within the housing 20 and 30 which are made of molded resin, such as ABS (acrylonitrile-butadien-styrene) resin. Thus, the effect of external static electricity on the laser diode is reduced so that the possibility of damage to the laser diode is reduced during the replacement of the VLD module and the reliability of the VLD module is increased.
Further, the lens holder is also contained within the housing 20 and 30 to reduce an external force on the lens holder. This feature of the invention is advantageous in that the lens holder does not move during the replacement of the VLD module 15, which prevents a change in the diameter of the laser beam.
With reference to Figures 19 to 21, the optical unit 14 includes a housing portion 14a and cover 14b which are connected to each other to provide a housing of the optical unit 14. In particular, the housing portion 14a and the cover 14b are sealingly connected at line 83 so that dust or small particles cannot enter therethrough. The cover 14b includes first and second openings 11 and 12 which are sealingly and transparently covered by first and second glass plates 81 and 82, respectively. In this embodiment, first and second scanning beams propagate through the first and second glass plates 81 and 82, respectively.
The VLD module 15 is secured to the top of the housing portion 14a of the optical unit 14 by screws 16 (Figures 19 and 20). The damper 17 between the VLD module 15 and optical unit 14 (Figure 20) prevents dust from entering the optical unit 14 through a possible gap therebetween, and prevents vibration of the scanner from being transmitted to the VLD module 15.
With reference to Figure 22, provided on the back wall of the housing portion 14a is a horizontal protrusion 91 for positioning the VLD module 15. Adjacent to the horizontal protrusion 91, an aperture 92 (Figures 25 and 26) is provided through the outer wall to open into inside of the housing of the optical unit 14. An aperture 95 (Figure 23) is provided through the condensing concave mirror 94 at the center thereof so that the apertures 92 and 95 provide a passage through which the laser beam propagates from the VLD module 15, which is mounted to the housing.portion 14a of the optical unit 14, to the polygon mirror 95.
In this particular embodiment, the aperture 92 is closed by a glass plate 92a (Figure 24) which is attached to the inner surface of the housing portion 14a. In particular, the glass plate 92a is obliquely provided relative to the optical axis of the VLD module 15 to prevent total reflection of the laser beam at the glass plate. In another embodiment of the invention, the aperture 92 may not be closed by the glass plate 92a since the damper 71 prevents dust from entering.
With reference to Figure 23, the laser beam entering the optical unit 14 through the apertures 92 and 95 is reflected by the rotating polygon mirror 93, which includes four mirrors in this embodiment, so that the beam scans the mirrors 96a to 96h. The scanning beam from the polygon mirror 93 is divided into a set of scanning beam segments when the beam scans the respective mirrors 96a to 96b so that a set of scanning lines are provided outside of the scanner. In this context, the mirrors 96a to 96h are referred to as beam dividing mirrors in this specification. In particular, according to the embodiment, the dividing mirrors 96a to 96h are oriented to produce first and second sets of scanning lines outside of the scanner through the first and second openings 11 and 12, respectively. Another set of beam dividing mirrors may be provided and attached to the cover 14b.
The scanning beam is diffusely reflected by a bar code. A portion of each reflected beam returns along the coincident light path of the emitted beam. Thus, the return beam is reflected by the polygon mirror 93 toward the aperture 95 which is provided through the concave mirror 94 for condensing the return beam onto the optical sensor 98. The optical sensor 98 generates an electrical signal corresponding to the return beam to a signal processor (not shown).
As mentioned above, the laser diode 62 is directly oriented to the polygon mirror 93 without a additional small mirror which is often provided around the concave mirror in some previously-proposed scanners. Thus, in an embodiment of the present invention, positioning between the laser source 63, additional mirror, and the polygon mirror 93 is not necessary.
The aperture 92 is obliquely formed in the housing portion 14a as shown in Figure 24 so that the laser beam runs to the polygon mirror 93 along a line which slants from vertical line. The polygon mirror 93 reflects the beam vertically toward the dividing mirrors 96a to 96h.
Figures 25 and 26 show a top and sectional views of the housing portion 14a, respectively, to which the VLD module 15 is mounted. The aperture 92 is provided substantially at the center of the housing portion 14a.
With reference to Figure 27, the housing portion 14a has a recess 103 on the outside surface of the back wall thereof. The recess 103 accommodates a control circuit board (not shown) for controlling the operation of the scanner. The circuit board 61 of the VLD module 15 is connected to the control circuit board by a flat cable 101.
Figures 28 and 29 are a side and top views of the housing portion 14a. The control circuit board and the VLD module cannot be directly connected to each other since the surface including the recess 103 to which the control circuit board is mounted and the surface to which the VLD module 15 is mounted are substantially perpendicular to each other as shown in Figures 28 and 29. Therefore, the control circuit board and the VLD module 15. are connected through the flat cable 101. The provision of the connector 66 outside of the housing 20 and 30 facilitates the attachment of the flat cable 101 to the connector 66.
With reference to Figure 29, one end of the flat cable 101 is connected to the connector 66 and the other end 102 is connected to the control circuit board.
Figures 30 to 32 show enlarged details of the VLD module 15 mounted to the housing portion 14a. The VLD module 15 emits the laser beam as shown by an arrow B as shown Figure 31. The damper 17 includes a passage 17a along which allow B which allows the laser beam propagates through the damper into the aperture 92.
As mentioned above, according to a previous proposal, a VLD module is provided within the optical unit 14. Thus, the VLD module must be formed as small as possible. For this purpose, the VLD module includes a laser diode only included in a housing, and necessary electrical circuits, such as an electric voltage transformer, a driver circuit and an output control circuit, are provided outside of the VLD module.
Figures 33 and 34 show block diagrams of electrical circuitry for a VLD module embodying the present invention and a previous proposal, respectively. According to the previous proposal, electric power is supplied to the laser diode (VLD) from a power source 110, such as a commercial electric line, through a transformer circuit, a driver circuit and output control circuit for the laser diode which are provided on a board 120 separate from a VLD module 122 as shown in Figure 34. In an embodiment of the present invention, a driver circuit and a output control circuit are provided on an additional board 114, which also corresponds to the circuit board 61, separate from a board for a transformer circuit 112 (Figure 33). The circuit board 61 is contained within the housing 20 and 30 to provide the VLD module 15.
As mentioned above, the power of the beam emitted from a laser diode relative to the input electric current is not uniform from one laser diode to another. According to the previous proposal, the driver and output control circuits are separately provided from the VLD module. Therefore, the output of the laser diode must be adjusted through the adjustment of the input electric current by the variable resistor 65 and must be carried out wherever the VLD module 15 is replaced. On the other hand, according to an embodiment of the present invention, the VLD module 15 includes the driver and output control circuits in the VLD module 15. Thus the adjustment of the output of the laser diode 62 can be carried out in a factory whereby the work and time for maintenance is reduced.

Claims

A light source module (15) comprising:
a laser diode (62) for emitting a laser beam;

a circuit board (61) including the laser diode (62), a driver circuit for the laser diode (62), and a connector (66) for receiving a power supply for driving the laser diode (62) from an electric power source;

means (53a, 54) for shaping the laser beam emitted by the laser diode (62), which beam shaping means (53a, 54) comprise a lens (54) for condensing the laser beam emitted by the laser diode (62) and means (53) defining an aperture (53a) through which the laser beam propagates from the lens (54) ;

a housing (20, 30) for containing the beam shaping means (53a, 54) and the circuit board (61) except for a portion of the circuit board (61) where the connector (66) is mounted;

a mount (40) for securing the circuit board (61) inside the housing (20, 30); and

a lens holder (50) for holding the optical axis of the lens (54) in alignment with the aperture (53a);
characterised in that:
the housing (20, 30) is made of electrically insulating material;

the mount (40) includes a bore (42) extending through the mount (40) to open to the laser diode (62) on the circuit board (61); and in that

the lens holder (50) is fitted into the bore (42) of the mount (40) to slide along the bore (42), the movement of the lens holder (50) within the bore (42) along the longitudinal axis of the bore (42) adjusting the position of the focal point of the laser beam.
A light source module according to claim 1, in which the housing (20, 30) is made of molded resin.
A light source module according to claim 1 or 2, further comprising means (43, 64) for locking the lens holder (50) relative to the mount (40).
A light source module according to any preceding claim, in which the circuit board (61) includes means (65) for adjusting the output of the laser diode (62).